Apache APISIX is built upon the shoulders of two giants:

NGINX, a widespread open source reverse-proxy
OpenResty, a platform that allows scripting NGINX with the Lua programming language via LuaJIT

This approach allows APISIX to provide out-of-the-box Lua plugins that should fit most business requirements. But there always comes a time when generic plugins don’t fit your requirements. In this case, you can write your own Lua plugin.